Billing for Dollars

Without a bill, a duck couldn't eat, nor could the carriers' employees and shareholders. The challenges of generating the information required to bill a subscriber in wireless are different than in landline systems. Although some capabilities, such as third-party billing and collect calling, are not necessary in wireless, some new ones, such as roaming and handoff, have no counterpart in older telecommunications systems.

When people think of billing, they most often think of carriers billing their subscribers, but settlement among carriers is just as important. Both billing and settlement are supported in wireless systems by the same underlying infrastructure. This is based on the exchange of CIBER (cellular intercarrier billing exchange record) records, as well as various proprietary formats.

CIBER is a collection of record formats that have been used for recording wireless intercarrier billing or settlement information since 1988. Different formats are used for recording airtime for a local call, airtime and toll for a long-distance call, intercarrier handoff of one party in a call and for additional charges that may be incurred (such as daily roaming fees). Cibernet, a subsidiary of CTIA, maintains the record format.

SIMPLE BUT EFFECTIVE CIBER's structure is primitive compared with more advanced protocols such as TIA/EIA-41, which is used for intersystem operations, and TIA/EIA-124, a protocol that also can convey billing records. Yet, perhaps CIBER's simplicity is one of its advantages and the secret of its longevity. Although CIBER is not often modified, it can be when necessary. The latest modifications went into effect in August, when support for LNP, intertechnology roaming and improved support for international roaming were added.

Furthermore, it is important for a billing protocol to be precise, unambiguous and robust. It is difficult to have a precise definition of a complex protocol, in which case, ambiguity often results. TIA/EIA-41, for example, has suffered from this problem. CIBER is robust because each record represents a single item for billing or settlement (or both). It is not necessary to perform buffering and merging of records. TIA/EIA-124 is not as simple, which may account for its lack of acceptance.

When a wireless phone is used to place a call in its home system, the MSC serving the call generates a call detail record (CDR) in a format that is usually proprietary to the MSC manufacturer. Traditionally, these records were sent on magnetic tape to a billing system, but increasingly they are being sent over a network. The billing system then can generate a line item or perform other operations (such as keeping track of monthly free minutes) for a subscriber's next bill.

TRICKY SITUATIONS But life is rarely simple. One complication could be that the home MSC starts to lose the signal from the mobile and needs to hand it off to a neighboring MSC. In this case, the home MSC still will generate the bill, so billing is not affected. However, the neighbor MSC has provided facilities to serve the call following the handoff and may expect to be reimbursed. If traffic between two MSCs is relatively symmetrical, it may be simpler and cheaper to use a "bill and keep" method that requires no settlement.

If traffic is asymmetrical, some form of settlement likely will be used. In this case, the system receiving the handoff generates a CDR, which is sent to its billing system. This generates a CIBER record that indicates the mobile's identity, the duration of the call and various other pieces of information, and forwards it to the home MSC's billing system. Later, the amount of money owed between carriers is settled. Rather than the carriers exchanging large checks, the amounts owed are subtracted, and the company that owes the most reimburses the other for the difference. Cibernet facilitates this process, which is known as net settlement. The settlement process is not tied directly to billing because the amount billed is not changed by the occurrence of an intersystem handoff during the call, and billing may occur before or after settlement.

Another common complication occurs when a mobile roams into a foreign system and is used to make a call. In this case, the home MSC is not involved in the call at all. At the end of the call, the visited MSC generates a CDR and sends it to its billing system. This billing system generates a CIBER record and forwards it to the home system. The home system will, as usual, generate the bill, but now will owe the visited system a portion of the revenue generated by the call.

LANDLINE VS. WIRELESS The ability to transmit information is only one aspect of billing and does not solve convergence or bill-presentation problems. However, this ability is an essential component. Looking forward, it is likely that that the transfer of CIBER records into other domains is a technical billing problem that will need to be solved.

One of the areas where wireless systems are deficient is in the provision of traditional intercarrier billing, providing services such as third-party billing, billing to a calling card and collect calling. Although wireline replacement has focused largely on the radio issues, it is necessary for the major landline billing services to be available on wireless systems before wireline replacement can be considered complete.

For example, when I recently dropped my two daughters off at the wrong location for a concert rehearsal, they had the presence of mind to call home -- collect. They would have been unable to call if a mobile had been my only phone. Providing these services requires crossing the hurdle of wireless/landline billing record exchange. Predictably, wireless systems rely on CIBER records, and landline systems on EMI/EMR records. Unfortunately, these two formats have little in common. A transparent billing-record exchange will be a major advance for wireless consumers.

TIA has published a new interim standard called Cellular Radiotelecommunications Intersystem Operations -- Over-the-Air Service Provisioning (OTASP) and Parameter Administration (OTAPA), TIA/EIA/IS-725-A.

This document presents Stage-1 recommendations for OTASP subscribers and OTAPA network feature descriptions. It also provides intersystem operation recommendations for supporting OTASP and OTAPA capability for CDMA and TMDA, with Stage-2 operations and scenarios, Stage-3 operations and parameter definitions, plus Stage-3 procedures.

The OTASP feature is intended to set down the process for the wireless industry to offer subscribers the convenience of activating new services or make changes in existing services securely without third-party intervention.

TIA also has published Mobile Center-Base Station Interface for Public Wireless Communications Systems, TIA/EIA-634-B. This document describes the overall system functions, including services and features, required for interfacing a base station with the MSC.

The standard is organized into a base part, TIA/EIA-634.000, and five subordinate parts. The base part contains all global references, definitions and terminology, as well as purpose, scope, organization and conventions. The 634.100 part contains the protocol common to all architectures supported by this standard; 634.200 contains the protocol descriptions that are unique to digital air interfaces when the service data unit (SDU) function is located at the source of the base station; 634.300 contains the protocol descriptions that are unique to digital air interfaces when the service data unit is remote from the SDU; 634.400 contains the message and element layouts and timer definitions for all parts of this standard; and 634.500 contains a description of interoperability between the two architectures supported by this standard.